netdev - Re: [PATCH net] net: remove hlist_nulls_add_tail

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Date:   Tue, 05 Dec 2017 18:07:26 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     kraigatgoog@...il.com, edumazet@...gle.com, glider@...gle.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net] net: remove hlist_nulls_add_tail_rcu()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 05 Dec 2017 12:45:56 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Alexander Potapenko reported use of uninitialized memory [1]
> 
> This happens when inserting a request socket into TCP ehash,
> in __sk_nulls_add_node_rcu(), since sk_reuseport is not initialized.
> 
> Bug was added by commit d894ba18d4e4 ("soreuseport: fix ordering for
> mixed v4/v6 sockets")
> 
> Note that d296ba60d8e2 ("soreuseport: Resolve merge conflict for v4/v6
> ordering fix") missed the opportunity to get rid of
> hlist_nulls_add_tail_rcu() :
> 
> Both UDP sockets and TCP/DCCP listeners no longer use
> __sk_nulls_add_node_rcu() for their hash insertion.
> 
> Since all other sockets have unique 4-tuple, the reuseport status
> has no special meaning, so we can always use hlist_nulls_add_head_rcu()
> for them and save few cycles/instructions.
> 
> [1]
 ...
> Fixes: d894ba18d4e4 ("soreuseport: fix ordering for mixed v4/v6 sockets")
> Fixes: d296ba60d8e2 ("soreuseport: Resolve merge conflict for v4/v6 ordering fix")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Alexander Potapenko <glider@...gle.com>
> Acked-by: Craig Gallek <kraig@...gle.com>

I was just talking with Craig and Willem about this change the other
day, what a coincidence :-)

Applied and queued up for -stable, thanks Eric.